In oil and gas exploration, several techniques are used to determine whether deposits of oil and/or natural gas exist at a particular site. One method to determine whether drilling operations should be continued at a particular site involves the analysis of gases contained within the drilling mud used in the drilling operation.
In most drilling operations, drilling mud is circulated around the drill bit during the drilling operation. This mud is circulated to the surface of the drill site and carries with it debris and cuttings resulting from drilling. As this mud surfaces to the lower atmospheric pressure, gases which have become trapped in the mud during drilling are released.
In the past, these gases have been analyzed to determine their hydrocarbon content. Knowing the presence and concentration of hydrocarbon gases in the drilling mud provides an indication of the formation confronted by the drill bit and provides a basis for determining the feasibility of obtaining oil and gas from the well.
In prior art devices used for detecting and analyzing these gases, highly sophisticated and temperamental equipment, generally employing a Wheatstone bridge arrangement, has been required to make the analysis. As a result, this equipment has normally been housed at a location remote from the drilling site in a controlled atmosphere. As a result of this remote positioning, these systems have required means for transporting gas released from the drilling mud to the analyzing apparatus. This has normally taken the form of delivery and return hoses and a vacuum system for drawing off the gases from the mud and delivering them to the detector. Such a vacuum system has normally required a pump either electrically or engine driven.
These systems have generally been unreliable and difficult to maintain. Gas detecting units at well sites are used in all types of weather conditions and must be operable twenty-four hours a day, seven days a week. Where the prior art units are operated in severe weather climates, such as subzero temperatures, the delivery lines to the system are frequently clogged by freezing of water vapor therein. Where freezing occurs, the units must be shut down and the lines thawed before the system can be made operable. Regardless of the weather conditions, these lines are subject to being clogged by debris or other contaminants drawn into the lines with the gases. Problems have also been encountered in preventing damage to the lines due to their proximity to the rigorous work environment around the drill site. The costs of the prior art units have been substantial because of the numerous components required, as well as the difficulty encountered in continuously maintaining such equipment and its components.
Thus, a need has arisen for a hydrocarbon detector unit for use in oil and gas drilling operations which is substantially simpler, more reliable and provides a high sensitivity at a reduced cost.